High performance and stable perovskite solar cells using vanadic oxide as a dopant for spiro-OMeTAD

Spiro-OMeTAD as a hole-transport material (HTM) plays a crucial role in the photovoltaic performance and stability of perovskite solar cells (PSCs). However, the inferior conductivity and mediocre hole-mobility of unoxidized spiro-OMeTAD limit its function. In order to improve the functional properties of HTMs, we develop a new kind of dopant, vanadic oxide (V 2 O 5 ) in place of the traditional oxygen in the presence of a lithium salt. V 2 O 5 with strong redox potential can rapidly oxidize spiro-OMeTAD, which effectively improves the hole-transport properties and adjusts the energy level of the HTM. Consequently, the champion PSC based on the V 2 O 5 -doped HTM achieves a power conversion efficiency of 20.5%, while the device without V 2 O 5 doping exhibits an efficiency of 18.1% under the same test conditions. Meanwhile, owing to the reduction of trap state density and the band gap adjustment by V 2 O 5 doping the hysteresis of devices is effectively suppressed and the stability is improved. The facile and inexpensive treatment and obvious performance improvement render the present finding very promising. Perovskite solar cells with vanadic oxide doping achieve a power conversion efficiency of 20.5%.